Multi-channel code-division multiplexing in front-end integrated circuits

Abstract

A challenging problem is maintaining low power consumption in multi-channel (MC) systems, where multiple input signals demand several front-end analog signal-processing blocks to be replicated. A code-division multiplexing (CDM) system can be generalized as a signal compression-decompression involving an analog-to-digital converter (ADC). This invention utilizes CDM in MC front-end integrated circuits to significantly reduce the power consumption of such systems. The invention also extends CDM's data compression advantages to uncorrelated and weakly correlated MC signals through the introduction of a new Multi-Channel Signal Binning and Multiplexing (MCSBM) method and architecture. The proposed method achieves significant reductions in power consumption in comparison to a conventional time-division multiplexing quantizer, while adding only a modest amount of overhead and complexity. Among other advantages, the invention permits architects to fabricate MC integrated circuits with ultra low power consumption and small chip area, where conventional architectures could not. Another embodiment of the invention relates to the system's compressor organizing samples of the input signal in such a way that the downstream ADC quantizes the higher variance samples with a higher resolution compared to the resolution it uses to quantize other samples with lower variance.

1. A multi-channel signal system, comprising:
 a plurality of code modulators for receiving a plurality of input signals, wherein each code modulator modulates with a unique code one of said plurality of input signals to output a code-modulated signal; 
 a signal summer coupled to each of said plurality of code modulators that combines the code-modulated signals into a combined signal; 
 a shared processing block coupled to the signal summer for processing the combined signal; 
 a plurality of matched filters coupled to the shared processing block, wherein each matched filter includes a code corresponding to one of the unique codes for recovering the corresponding input signal from the combined signal; 
 an initial sample-and-hold block that sequentially samples and holds a single input channel and outputs one of N number of samples of the single input channel to each of N number of delay blocks, coupled to said sample-and-hold block; 
 wherein the n-th delay block delays the multiplexing process of its output sample by N−n clock cycles; and 
 wherein said plurality of delay blocks output the plurality of input signals for receipt by the plurality of code modulators. 
 
     
     
       2. A multi-channel signal system, comprising:
 a plurality of code modulators for receiving a plurality of input signals, wherein each code modulator modulates with a unique code one of said plurality of input signals to output a code-modulated signal; wherein each code modulator also turns on or off depending on its input signal's activity; 
 a signal summer coupled to each of said plurality of code modulators that combines the code-modulated signals into a combined signal; 
 a shared processing block coupled to the signal summer for processing the combined signal; 
 a plurality of matched filters coupled to the shared processing block, wherein each matched filter includes a code corresponding to one of the unique codes for recovering the corresponding input signal from the combined signal; and 
 an analog-to-digital converter with adaptable resolution and bandwidth based on the number and locations of the active input signals, that quantizes the combined signal from the shared processing block and outputs the quantized combined signal to the plurality of matched filters for recovery of the original input signals. 
 
     
     
       3. The multi-channel signal system of  claim 2 , further comprising:
 an initial sample-and-hold block that sequentially samples and holds a single input channel and outputs one of N number of samples of the single input channel to each of N number of delay blocks, coupled to said sample-and-hold block; 
 wherein the n-th delay block delays the multiplexing process of its output sample by N−n clock cycles; and 
 wherein said plurality of delay blocks output the plurality of input signals for receipt by the plurality of code modulators. 
 
     
     
       4. A multi-channel signal binning and multiplexing system, comprising:
 a plurality of sample-and-hold blocks for receiving a plurality of input signals; 
 a difference comparison network, coupled to the sample-and-hold blocks, that extracts the difference in signal amplitude between the input signals; 
 a plurality of comparators, coupled to the difference comparison network, that provides information on whether or not the differences in signal amplitude exceed a settable threshold voltage; 
 a Hadamard multiplexer-and-selector, coupled to the sample-and-hold blocks, that code-division multiplexes each of a plurality of bins containing one or more of the input signals based on the information on the multi-channel input signal amplitude differences, and outputs a code-division multiplexed output signal; wherein each said bin is a mutually exclusive subset of the plurality of input signals; 
 an analog-to-digital converter that quantizes the code-division multiplexed output signal; 
 a plurality of matched filters, coupled to the analog-to-digital converter, that demultiplex the quantized code-division multiplexed output signals; and 
 a signal reorganizer, coupled to the matched filters, that sorts the output signals of the matched filter to achieve the recovered multi-channel input signals. 
 
     
     
       5. The multi-channel signal binning and multiplexing system of  claim 4 , wherein said analog-to-digital converter quantizes one or more code-division multiplexed output signals with high variance at a first resolution, and quantizes one or more code-division multiplexed output signals with lower variance with a second resolution lower than that of the first resolution. 
     
     
       6. The multi-channel signal binning and multiplexing system of  claim 4 , further comprising:
 a variable gain amplifier, coupled to the analog-to-digital converter, that adjusts the code-division multiplexed output signal to the desired scale of the analog-to-digital converter. 
 
     
     
       7. The multi-channel signal binning and multiplexing system of  claim 6 , wherein said analog-to-digital converter quantizes one or more code-division multiplexed output signals with high variance at a first resolution, and quantizes one or more code-division multiplexed output signals with lower variance with a second resolution lower than that of the first resolution. 
     
     
       8. The multi-channel signal binning and multiplexing system of  claim 4 , further comprising:
 an initial sample-and-hold block that sequentially samples and holds a single input channel and outputs one of N number of samples of the single input channel to each of N number of delay blocks, coupled to said sample-and-hold block; 
 wherein the n-th delay block delays the multiplexing process of its output sample by N−n clock cycles; and 
 wherein said plurality of delay blocks output the plurality of input signals for receipt by the plurality of sample-and-hold blocks. 
 
     
     
       9. The multi-channel signal binning and multiplexing system of  claim 8 , wherein said analog-to-digital converter quantizes one or more code-division multiplexed output signals with high variance at a first resolution, and quantizes one or more code-division multiplexed output signals with lower variance with a second resolution lower than that of the first resolution. 
     
     
       10. The multi-channel signal binning and multiplexing system of  claim 8 , further comprising:
 a variable gain amplifier, coupled to the analog-to-digital converter, that adjusts the code-division multiplexed output signal to the desired scale of the analog-to-digital converter. 
 
     
     
       11. The multi-channel signal binning and multiplexing system of  claim 10 , wherein said analog-to-digital converter quantizes one or more code-division multiplexed output signals with high variance at a first resolution, and quantizes one or more code-division multiplexed output signals with lower variance with a second resolution lower than that of the first resolution. 
     
     
       12. A compression-decompression analog-to-digital converter system, comprising:
 at least one signal compressor for receiving one or more input signals and outputting samples of said input signals to one or more analog-to-digital converters; 
 wherein each said compressor's output sample signals are organized based on their variance; 
 wherein each said analog-to-digital converter quantizes any higher variance output sample signals with higher resolution than the resolution at which it quantizes any output sample signals with lower variance; and 
 a signal decompressor coupled to each said analog-to-digital converter, that receives one or more quantized output sample signals therefrom, re-organizes said one or more quantized output sample signals, and reconstructs said one or more quantized output sample signals into a reconstructed signal. 
 
     
     
       13. A multi-channel signal binning and multiplexing method, comprising the steps of:
 organizing each from a plurality of input signals into one from a plurality of bins of similar amplitude, determined by a settable threshold voltage difference between the input signals' amplitudes; 
 modulating each resulting bin of input signals with a unique code to output a corresponding bin containing code-modulated output signals; 
 quantizing each bin of code-modulated output signals according to variance of the signals contained therein; 
 recovering each bin of input signals by demodulating the quantized code-modulated output signals with a code corresponding to the unique code by which each bin was modulated; and 
 reorganizing the recovered signals to get the original multi-channel input signals. 
 
     
     
       14. The multi-channel signal binning and multiplexing method of  claim 13 , wherein one or more unique codes used in the modulating step is a binary code. 
     
     
       15. The multi-channel signal binning and multiplexing method of  claim 13 , wherein one or more unique codes used in the modulating step is a M-ary code. 
     
     
       16. The multi-channel signal binning and multiplexing method of  claim 13 , wherein the modulating step is performed by multiplying each bin of input signals with a non orthogonal matrix to output a corresponding bin containing code-modulated output signals. 
     
     
       17. The multi-channel signal binning and multiplexing method of  claim 13 , wherein the modulating step is performed by multiplying each bin of input signals with an orthogonal matrix to output a corresponding bin containing code-modulated output signals. 
     
     
       18. The multi-channel signal binning and multiplexing method of  claim 17 , wherein the
 orthogonal matrix used in the modulating step is a Hadamard matrix. 
 
     
     
       19. A compression-decompression analog-to-digital converting method, comprising the steps of:
 sampling one or more received input signals; 
 organizing each sample based on its variance; 
 quantizing from analog into digital form one or more samples with high variance at a first resolution; 
 quantizing from analog into digital form one or more samples with lower variance than those with high variance, with a second resolution different from that of the first resolution; 
 re-organizing the quantized samples. 
 
     
     
       20. The compression-decompression analog-to-digital converting method of  claim 19 , further comprising a step for reconstructing the re-organized quantized samples into a reconstructed signal. 
     
     
       21. The compression-decompression analog-to-digital converting method of  claim 19 , wherein the second resolution in the second quantizing step is lower than the first resolution in the first quantizing step. 
     
     
       22. The compression-decompression analog-to-digital converting method of  claim 21 , further comprising a step for reconstructing the re-organized quantized samples into a reconstructed signal.